Twin-engine helicopters typically require both engines to operate at a relatively high power output during some phases of flight such as during take-off, for example. During other phases of flight such as cruise, power requirements may be significantly lower and therefore the power output from each engine may be significantly reduced. Even though only one of the two engines may be required during such other phases, it is typically required for safety reasons that both engines remain operating at all times during flight. In an emergency condition such as failure of one of the two engines, this allows the other engine to rapidly increase its power output to make up for the failed engine and take over. When the helicopter is at low altitude, it is imperative that the power output increase by the remaining engine be done as rapidly as possible.
When both engines of a dual-engine helicopter are operating at reduced power output, they are typically not operating within an optimum performance window of the engines. Consequently, depending on the type of mission, both engines of the helicopter operating at a reduced power output setting may operate at a relatively low fuel efficiency (i.e. relatively high fuel consumption) for relatively long portions of a flight.
Improvement is therefore desirable.